1. Field
This disclosure relates generally to integrated circuits, and more specifically, to a packaged integrated circuit
2. Related Art
One of the techniques that has been used for increasing the density of circuits on a printed circuit board is to stack the integrated circuits, which are also commonly called stacked die package. This is also desirable when two integrated circuits function closely together but are preferably made differently. One example is an rf integrated circuit that has rf functions and another integrated circuit in which information is coupled back and forth between them. The processes used for optimizing the logic device are different from the processes used in optimizing the rf device. One of the techniques for stacking has been to stack integrated circuits and couple them together by bumps or wire bonding. This can be effective, but a disadvantage is that often it is difficult to adequately test the integrated circuits prior to packaging sufficiently to ensure that they operate as required. Testing at the integrated circuit level prior to packaging when still part of a wafer, typically called wafer probe, is effective to an extent but generally does not allow for sufficient testing to ensure that the integrated circuit will be meet all of the performance requirements. Thus, when stacking integrated circuits, the complete testing is not done until after all of the die are stacked and packaging is complete. When this happens, if any one of the die are defective, the whole package is then defective. There may or may not be a possibility of rework to salvage the good die, but any such rework is likely to be expensive and time consuming as well as risk making the remaining good ones into defective ones. The package on package techniques tend to be limited in applicability to using die of the same size and function or having an excessively large base. They may even require further packaging.
Thus, there is a need for ability to provide integrated circuits with the ability to be interconnected that improve one or more of the existing difficulties.